The early proteins of SV-40 large T antigen and small t antigen are model viral oncogenes and have been studied from both biochemical and genetic approaches. We propose to search for cellular components which may interact with these viral products through the continuation of a broad based program. Specifically, we propose to: 1. Obtain cell lines which have reverted from oncogenic transformation. These lines may habor mutation in genes required for transformation. The appropriate revertants may be used as tools for cloning these putative cellular genes via transfection protocols. 2. We would like to know if certain cellular sequences which bind viral T antigen are linked to genes which may be induced by SV-40, and more generally, we have designed transient expression assays to ask if T binding to DNA is a positive activator or heterologous promoters. 3. Clone c-DNA copies of rare mRNA species that are expressed at elevated levels in SV-40 transformed cells. 4. Study the nature of cell cycle regulated expression of the cellular Tk gene, as a model gene which is indirectly or directly induced by acute viral infection.